The present invention relates to a cutter mainly for synthetic resin workpieces, and more particularly to a cutter for cutting synthetic resin articles such as polyvinyl chloride or like synthetic resin pipes and tubes for water supply systems, power cables and telephone cables.
Synthetic resin articles are cut usually by the following methods.
1. With use of saw
With use of a saw, workpieces are difficult to cut quickly and easily, while the saw leaves traces of saw teeth on the cut end, creating a rugged face which must be smoothened. The cutting operation therefore requires a cumbersome procedure.
2. With use of scissors
According to this method, workpieces are cut in a snipping manner with a pair of cutting blades which are movable past one another. Since the opening and closing movement of the handles is converted directly to the opening and closing of the blades, the cutting operation requires a great force and it is impossible to use the scissors only with one hand. The cutting blades, which will not bite into the workpiece easily, must be given an excess force when starting to cut the workpiece, possibly cracking or otherwise deforming the workpiece at or near the cutting portion. Additionally the cutting blades are likely to leave a stepped portion on the cut end face when deviating from each other in the course of cutting, thus necessitating a finishing procedure to smoothen the cut end.
3. With use of cutter of the single blade type
FIG. 11 shows a cutter of this type. The opening and closing movement of handles 51 and 52 is converted to the turn of a cutting blade 53 about a pivot 54 to cut a workpiece supported on a holder portion 51'. When the handles are opened and closed, an engaging projection 56 on the distal end of an operating rod 55 engages in one of cutouts 58', 58" and 58'" successively in the order mentioned which cutouts are formed in a recess 57 in the base portion 53' of the cutting blade 53, turning the cutting blade 53 about the pivot 54 in the direction of the arrow shown. With this construction, therefore, the force required for cutting (i.e. gripping force to close the handles 51 and 52) progressively increases as the distance between the pivot 54 and the projection 56 decreases, presenting difficulty in opening and closing the handles by one hand.